The present invention relates to a device for synchronizing processes which are executed on a plurality of units, in particular, in paper-processing machines and a method for synchronizing a plurality of such units.
Printing presses have a plurality of rotationally movable parts which have to be set into rotary motion in an angularly synchronous manner. To this end, in the past, these parts to be rotationally driven were coupled via a mechanical connection as, for example, a line shaft or a continuous gear train, which, however, had the disadvantage, among other things, that unpleasant vibrations occurred in such a machine. Therefore, recently the trend for the printing press parts to be rotationally driven is no longer to be mechanically synchronized with perfect angular accuracy but to be provided with separate electric drives which are then synchronized with each other via an electronic control. To this end, however, electronic circuits are required which correct the separate drive motors in such a manner that they work in an angularly synchronous manner. Moreover, the electronic controllers have to work rapidly and accurately. As a rule, greater difficulties occur especially when changing the operating speed of a printing press or of parts of a printing press. In this case, it must be ensured that the individual electric drives continue to work in an angularly synchronous manner after the speed change.
A method and corresponding device for controlling the exact angular synchronism of a plurality of electric drives is known from German Patent DE 197 27 824 C1. This system is composed of a control computer, which represents a central master system, and a plurality of distributed drive controllers, which are arranged near the electric drive to be controlled. In this context, the distributed drive controllers and the master computer are interconnected via a synchronization bus. In this connection, the master system supplies machine speed setpoints to the distributed drive controllers via the synchronization bus. The rotational speed setpoints are locally generated from these machine speed setpoints in the respective distributed drive controllers. To allow angular synchronization between the individual drive units, the distributed drive controllers contain angle setpoint generators which are composed of a master pointer in the respective drive controller. When the machine speed setpoints have now been distributed to the drive controllers via the synchronization bus, then the master system sends a so-called “interrupt” to all drive controllers. This interrupt is used for synchronization and ensures that all distributed drive controllers run their computing cycles with the same current machine speed setpoint. The appropriate rotational speed and angle setpoints for the respective drive are then calculated in the distributed drive controllers. Such a drive control system for synchronizing a plurality of drive units offers the advantage that the synchronization bus is relieved since it only has to distribute the common machine speed setpoints and interrupts. Moreover, it is proposed to send so-called “asynchronous setpoint values”, such as an offset angle between several drive units, over a separate bus which is exclusively responsible for control and parameterization data.